In a Global Positioning System (GPS), four or more GPS satellites per plane are positioned in six orbital planes with each GPS satellite crossing the equator of the Earth at an inclination angle of 55 degrees in order to maximize user coverage anywhere on the Earth's surface. Each GPS satellite circles the earth approximately every 12 hours to transmit navigation messages.
A GPS receiver receives the navigation messages periodically transmitted from at least four or more GPS satellites out of a plurality of GPS satellites. The GPS receiver detects a distance between the receiver and the GPS satellites, and a position vector (3D location coordinate) of the GPS satellites to calculate its position vector.
In a navigation system equipped with the GPS receiver, the position vector detected by the GPS receiver is map-matched on a digital map to be displayed on a display screen. As a value-added service, the navigation system provides a travel route guidance service notifying a user's current position or a travel route from a starting point to a destination. Accordingly, the user of the navigation system can easily find a destination from a starting point or a current location by receiving the travel route guidance service of the navigation system.
Recently, navigation systems have been mounted to various mobile terminals, such as a portable terminal, a personal digital assistance (PDA), an iBook phone, and a smart phone. Hereinafter, the mobile terminal is simply referred to as a portable terminal for convenience. Thus, a user can be guided by a travel route to a destination even if the user walks to the destination on foot.
If a user of a portable terminal equipped with a navigation system is provided with a service for guiding the user to a predetermined destination on a travel route, the user typically has to check for an actual object on the street to correspond to an object displayed on a digital map on a display of the portable terminal.
In this case, the user has to visually check and match one-by-one the object on the map with the actual object on the street. For example, the user would have to match a building that he or she actually sees on the street with that shown on the digital map to make sure that a prescribed building (“A”) displayed on the screen is identical to an actual building. Thereafter, discrimination is made as to which building on the map actually corresponds to the building “A” on the screen.
Particularly, if an object building is located far away from a current location of a user, the user has to personally move to a location of the object building in order to obtain information of the object building. By moving to the location of the object building, the user can confirm that the building wanted by him or her corresponds to the object building on the map only if the information obtained on the object building matches the building displayed on the map.
Furthermore, if a user moves to a destination by receiving a travel route via a navigation system disposed on a portable terminal, the navigation system typically displays a map on a screen and guides the user onto the travel route. As a result, the user has to find a destination by checking buildings on the map one-by-one with the actual object building on the street.